Solid State Drives have really come into their own over the past couple of years, as evidenced by the fast growing adoption rate amongst enthusiasts and prosumers. Hard drives have traditionally been the bottleneck in a PC, and fast NAND flash access speeds can make even an obsolete system shine. However, not everyone can afford the pricey cost of SSDs or their capacity limitations. The answer for this is hybrid hard drives.

Hybrid hard drives combine high-density, large capacity platters with NAND flash memory. This allows it to combine the fast access speeds of NAND with the cheap bulk storage of magnetic media while keeping costs under control. However, the secret sauce is in the NAND flash controller and the firmware; if either is not up to par, the entire drive will underperform.

Seagate is one of the few companies in this market, and is releasing today their third generation of hybrid hard drives for the laptop market. The Seagate Momentus XT is a 2.5 inch 750GB hard drive paired with 8GB of Single Level Cell (SLC) NAND flash.

Seagate's first attempt at a hybrid hard drive was the Momentus PSD in 2007. That product was a disastrous flop. It had only 256MB of NAND flash, far too small to be useful. Its 5400RPM platters led to lackluster access times. The NAND controller and firmware were problematic, and costs were high. The resulting low performance kept customers away.

The company tried again last year with the all new Momentus XT. A 4GB SLC cache, new proprietary controller, and rewritten firmware showed off a whole new direction. The NAND was used as a fast cache, with new adaptive algorithms powering the drive to near SSD performance levels. In many ways, this is the strategy used by Fortune 500 companies which have adopted tiered storage solutions. SSDs are used to cache frequently accessed data, while much cheaper hard drives store long-term data.

The second generation Momentus XT doubles the SLC cache to 8GB, while dual platters provide 750GB of storage. This will be the only version of the drive, as capacity trumps cost in this segment. The 500GB Momentus XT accounted for over 90% of sales in the first generation, and will continue to be sold.

A proprietary NAND flash controller has once again been used, but it incorporates evolutionary improvements made by Seagate. This combined with improved "Adaptive Memory" firmware has led to boot speeds comparable to current generation SSDs. There is no TRIM support, but the NAND controller provides a similar function during its garbage collection. The magnetic storage portion itself has a dedicated 32MB DDR2 cache, but we were unable to get details on the NAND controller's RAM. A 6Gbps SATA connection is needed for optimal performance thanks to an improved data burst speed.

The 2.5-inch drive has a height of 9.5mm, which will limit its use in netbooks and tablets. The drive come formatted for the Advanced Format 4K (4096-byte) sector size, and will require a clean installation for best performance.

The original price was supposed to be set at $189, but was raised in the middle of last week to $199. Now the price has been set at $245 due to extreme demand. Seagate has been shipping in volume for the last week, but the huge demand has caught the company off guard. Normally the company would be able to increase production, but resources are strained due to component shortages caused by the floods in Thailand.

The drive is available today in volume at online retailers Amazon, Canada Computers, CDW, Memory Express, NCIX, Newegg, and TigerDirect. Channel orders have been high, with many e-tailers expecting these drives to be used as performance upgrade alternative to a new laptop due to tough economic times.

Seven OEMs are in the process or have already qualified the Momentus XT. This is a bit surprising considering the conservative nature of OEMs, but DailyTech has been told by Seagate that these OEMs see the drive as a major competitive advantage in their designs for high-end gaming laptops, while keeping costs in control.

Seagate has sold over 1 million hybrid hard drives already, and has plans for a third generation Momentus XT using Multi-Level Cell (MLC) NAND flash. This will allow it to greatly increase the amount of NAND while keeping costs in check.

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This article is over a month old, voting and posting comments is disabled

2.5 is no longer just a "laptop" form factor. Hell my Intel X-25's are 2.5 and that was like 3 years ago.

In a laptop application pure SSD's make even MORE sense over HDD's. Less power consumption, crazy fast load times, and lack of moving parts make a mobile device WAY more durable. It's not like most people need tons of storage capacity for a laptop anyway.